The experiment consisted of a randomized complete block design with four plots in
each of the three blocks. Each treatment (plot) was randomized within the block
and consisted of three rows with seven trees in each row. Treatments within each
block were separated by five trees down each row or by three rows of trees
between the treatments. The rows were oriented from north to south and were 3 m
apart. Therefore, two sheets of film were stapled together and placed over the
bare soil between the rows. For the treatments, the soil beneath the plot of trees
was completely covered by films.